Precision low-dose,low-waste syringes and ergonomic attachments therefor

ABSTRACT

Precision low-dose, low-waste syringe configurations have a reduced diameter lumen for dispensing 0.01 ml increments of contents. Plunger and lumen configurations and a needle interface eliminate dead space. Ergonomic attachments improve the control and precision of delivery of syringes. An attachment main body includes a gripping surface to permit a user to engage the attachment and move the attachment main body, and thus the syringe plunger relative to the syringe barrel using sliding movement. Optical enhancement features are provided on the attachment to improve the readability of gradations and plunger position. The attachment may be provided with an assist feature, which may be a traction wheel mounted on the attachment body. An alternative configuration suitable for syringe contents of higher viscosity may include a pair of toothed pinion gears on a wheel and which cooperate with respective toothed racks formed on or fastened to the syringe body.

This application is a continuation of application Ser. No. 16/120,122filed on Aug. 31, 2018, titled PRECISION LOW-DOSE, LOW-WASTE SYRINGESAND ERGONOMIC ATTACHMENTS THEREFOR, which claims priority to provisionalapplication Ser. No. 62/686,915, filed on Jun. 19, 2018. The subjectmatter of these applications is hereby incorporated herein by referencein its entirety.

FIELD

The disclosure relates generally to medical devices, including syringesfor controlling delivery of medications and biological fluids to apatient. The disclosure also relates to syringe configurations thatfacilitate precise delivery of very small volumes and/or doses and lowwaste of syringe contents. The disclosure relates further to attachmentsand adapters for improving the ergonomics of syringe operation and forenabling a user to precisely control the actuation of a syringe.

BACKGROUND

In some areas of medicine, there is trend towards lower volume, higherconcentration dosages of therapeutic compounds and drugs to be deliveredvia injection, typically by syringe. For example, in the cosmeticsurgery field, recent trends include procedures termed “High DoseMicro-focused” or “HDMF” injections of botulinum toxin, which mayinvolve the use of high concentration and relatively small deliveredvolumes of compounds or mixtures compared to the concentrations andvolumes that have, in the past, been typically used for such injectionsin cosmetic treatments and in very precise amounts and in very focused,localized areas of the human face and body. The cost of these compoundsand mixtures are relatively high to begin with. As the concentrationsincrease, the relative cost of wasted amounts of the compounds andmixtures also increases.

A number of problems in the prior art stem from the limitations ofexisting syringes to be adapted to precision, low dose/volumeapplications. For example, the ability to deliver precise volumes inincrements of as small as 0.01 ml may typically be required in suchapplications. Existing syringe configurations are not readily adapted toprecise control of delivery such small increments. A related problem isaccurate control and reading of syringes as the form factor becomesreduced. Still another problem is that prior art syringe configurationsmay demonstrate structural deficiencies when their form factor isreduced. More specifically, for example, reducing the plunger diametersignificantly to fit within a reduced syringe lumen may render theplunger susceptible to buckling or bending when a force is applied, thusaffecting syringe function and accuracy. Ergonomic factors, includinguser comfort and control and readability of syringe indicia and plungerposition also become a factor as the lumen diameter and other parametersare reduced.

Yet another problem is the need to reduce wasted residual amounts leftundelivered in the “dead space” of prior art syringes, as theconcentration of expensive substances, such as botulinum toxin in adelivery medium (solvent) increases, the cost of wasted amounts of themixture also increases. Another problem relates to the structuralshortcomings of traditional syringes when their form factor is reducedin size.

Yet another problem is the need for precise control of the dispensing ofsyringe contents, such as dermal fillers and other compositions that maybe of a relatively high viscosity.

It would therefore be advantageous to provide devices, includingsyringes and attachments that address the aforementioned shortcoming andothers in the prior art.

SUMMARY

According to one aspect of the disclosure, precision low-dose, low-wastesyringe configurations are provided for facilitating precise control anddelivery of syringe contents and for reducing or eliminating residualwaste. The syringe configurations may have a reduced diameter lumen suchthat a relatively long travel of the syringe plunger is undertaken fordispensing a given volume of syringe contents, which improves theprecision with which contents can be dispensed. Total syringe volume maybe on the order of 0.25 or 0.50 milliliters.

According to another aspect of the disclosure, an ergonomic attachmentis provided for improving the control and precision of delivery ofsyringes. The attachment may be used with syringes such as the low-dose,low-waste syringes described herein, or may be used with knowntraditional prior art syringes to improve the precision and controlthereof. A main body extends axially to a plunger engaging end and asyringe guide end. The plunger engaging end may include a receptacle forreceiving a thumb pad on the end of the syringe plunger. The guide endincludes a guide, which provides for sliding engagement with the syringebarrel. The main body includes a gripping surface to permit a user toengage the attachment with his or her fingers or thumb and to move theattachment main body, and thus the syringe plunger, relative to thesyringe barrel using sliding movement between the user's thumb andfingers. This mode of actuation provides improved control of thesyringe, enables the user to grip the syringe closer to the injectionpoint (needle end), provides stability to the syringe plunger, andprovides more accurate control of the delivery of syringe contents.

According to a further aspect, a syringe attachment is provided with anassist feature, which may be a traction wheel mounted on the attachmentbody. The traction wheel may provide a mechanical advantage, i.e.,leverage, to enable the user to move the attachment body, and thus thesyringe plunger, with high precision. A number of wheel mounting slotsmay be provided on the attachment body to enable a user to select acomfortable position. The attachment may be provided as a kit includinga number of wheels of various sizes to enable a user to configure theattachment according to their preference for comfort and control. Thewheel may be mounted for selective engagement with the syringe barrel.In one configuration, the main body may flex to permit the wheel toengage the syringe barrel when pressure is applied by the user's thumb.In another configuration, the wheel may be biased in an unengagedposition using springs or resilient elements in the mounting slots.

According to another aspect, an attachment is provided with features forgenerating audible or tactile indications to a user of a preciseincremental dose. A syringe body may be provided with raised gradationsformed therein and on a surface that is engaged by an assist feature onthe attachment. When the assist feature is rolled over each raisedportion, the user senses the tactile event and perceives that thesyringe plunger has moved one increment. Thus, more precise indicationand control is facilitated for even small movements of the syringeplunger.

According to another aspect, optical enhancement features are providedto improve the readability of gradations and plunger position. Smallgradations indicating incremental doses of as small as 0.01 ml may beprovided on the syringe barrel. A magnifying element, such as a prism orlens, may be incorporated into the attachment near the syringe guideend. A reference sight, which may be hairline indicator incorporatedinto the attachment and/or magnifying element, may be provided on theattachment guide end to indicate the position of the attachment, andthus the plunger and plunger end, relative to the gradations on thesyringe barrel. In this manner, very fine gradations may be indicated onthe syringe barrel and can be read in combination with the plungerposition to indicate very small incremental movements of the plunger.

According to a further aspect, syringes are provided which haveparticular suitability to low dosage applications. Overall syringevolumes of 0.25 ml or 0.50 ml require small lumen diameters and smallplunger diameters. The syringe barrel may be provided with gradationscorresponding to 0.01 ml incremental doses, resulting in 25 gradationson the 0.25 ml configuration and 50 gradations on the 0.50 ml syringe.The syringes may be provided with a thickened wall to facilitatehandling and control. A flat portion on the syringe barrel improves thereadability of the gradations and viewing of the syringe contents andplunger piston as well as operation with optical enhancements on anattachment that may contain an assist feature that facilitates precisecontrol of the plunger movement.

According to another aspect, syringe plunger configurations and needlehub/syringe interfaces with eliminated dead space. A lumen end wallextends into abutting engagement with an end surface of a needle hub.The plunger piston is provided with a flat surface such that the lumenis entire evacuated when the plunger is in its fully inserted positionand no waste material remains except in the small needle lumen. Thisresults in cost savings.

DESCRIPTION OF THE DRAWINGS

The above and other attendant advantages and features of the inventionwill be apparent from the following detailed description together withthe accompanying drawings, in which like reference numerals representlike elements throughout. It will be understood that the description andembodiments are intended as illustrative examples according to aspectsof the disclosure and are not intended to be limiting to the scope ofinvention, which is set forth in the claims appended hereto.

FIG. 1 is a perspective view of an example attachment, according toaspects of the disclosure, assembled on a syringe, according to aspectsof the disclosure.

FIG. 2A is an exploded view of the attachment and syringe combination ofFIG. 1. FIG. 2B is a detail view of a portion of FIG. 2A, as indicated.

FIG. 3 is a perspective view of the attachment and syringe combinationof FIG. 1, showing a different position of the attachment and syringeplunger.

FIG. 4. is a cross-section of the attachment and syringe combination ofFIG. 3 in the plane 4-4 in FIG. 3.

FIG. 5 is a cross-section of the attachment and syringe combination ofFIG. 3 in the plane 5-5 in FIG. 3.

FIG. 6 is a top view of a portion of the attachment and syringecombination of FIG. 3, showing a magnified view thru an optical element.

FIG. 7 is a perspective of a first alternative attachment configurationassembled on a syringe, the attachment being without an assist feature.

FIGS. 8A and 8B are cross-sections showing an example needle hub/syringeinterface and plunger seal advantageous for a syringe having a totalvolume of about 0.25 ml, with the plunger in a slightly open positionand a fully inserted position, respectively.

FIGS. 9A and 9B are cross-sections showing an example needle hub/syringeinterface and plunger seal advantageous for a syringe having a totalvolume of about 0.50 ml, with the plunger in a slightly open positionand a fully inserted position, respectively.

FIG. 10 is an exploded view of an attachment and syringe with theattachment having an optical element mounting component that isadjustable.

FIG. 11 is a perspective of second alternative attachment configurationassembled on a syringe.

FIG. 12 is an exploded view of the alternative attachment and syringecombination of FIG. 11.

FIG. 13 is a detailed perspective of a syringe guide end of thealternative attachment of FIGS. 11 and 12.

FIG. 14 is a bottom perspective of the attachment and syringecombination of FIG. 11.

FIG. 15 is a bottom perspective of the attachment of FIG. 11.

FIG. 16 is a perspective view of a third alternative attachment andsyringe combination.

FIG. 17 is a side view of the attachment and syringe combination of FIG.16.

DETAILED DESCRIPTION

FIGS. 1 and 2A show an assembled view and an exploded view,respectively, of an example syringe attachment 100 and syringe 200according to aspects of the disclosure. Attachment 100 may include anelongate main body portion 110, which extends from a syringe plungerengaging end 120 to an opposite syringe guide end 130. Main body portionmay include a gripping surface 112 which permits a user to apply asliding force on the attachment using the fingers and or thumb. Syringeplunger engaging end 120 may include a receptacle or slot 122 forreceiving a thumb pad or button 242 of the syringe plunger. An aperture124 may accommodate the plunger shaft 241. Receptacle 122 and/oraperture 124 may be sized to provide a friction fit around thumb pad 242and plunger shaft 241 to firmly retain the plunger relative to theattachment 100. FIG. 5 is a cross section that further illustrates anexample orientation of the syringe button 242 within the syringe plungerengaging end 120 of attachment. Syringe guide end 130 may include agenerally U-shaped syringe guide 135 that is shaped complementarily tothe outer surface of the syringe barrel 210 and includes an innersurface 136 that facilitates sliding movement along the syringe barrel210. Surface 136 may be provided with a friction reducing coating,lubricant or surface texture. A pair of opposed retaining edges 138 maybe formed in the guide end 130 to engage a flat portion of the syringebarrel to keep the attachment aligned with the syringe barrel (andplunger) axis and prevent lateral and upward movement of the syringebarrel 210 within the guide 135.

According to aspects of the disclosure, syringe 200 includes featuresfor facilitating the storage and delivery of very small incrementaldoses, including with a small diameter lumen, plunger diameter andplunger seal, while having an external form, i.e., outside diameter thatfacilitates easy handling. In this regard the barrel walls may be ofincreased thickness compared to prior art syringe configurations.Syringe barrel 210 may be provided with an internal lumen diameter thatprovides a total syringe volume of about 0.50 ml, with 50 gradationsindicated on the syringe barrel, or in another configuration, about 0.25ml, with 25 gradations indicated on the syringe barrel. With a syringelength of 4 inches with a 0.50 ml volume and 50 gradations, for example,each incremental 0.01 ml dose may require a controlled a plungermovement on the order of 0.08 inches. As will be appreciated by those ofordinary skill, the features of the syringe and attachments describedabove and further below herein will facilitate the small, precise andcontrolled movements of the syringe plunger for such small incrementaldoses.

Still referring to FIGS. 1 and 2A, syringe 200 may include a plungerreceiving end 230 having a flange 231 extending therefrom, forpermitting traditional operation of the syringe 200 using two fingers,one on each side of flange 231, and the thumb on syringe thumb pad 242.The flange 231 may include a recessed portion 232 to accommodate thewidth of attachment 100. The syringe wall thickness and material arechosen to provide a view of the syringe plunger piston 250.1 within thelumen as viewed thru the flat portion 211 of the syringe barrel 200. Aneedle receiving end 220 of the syringe may engage a needle hub 260 in amanner that will be described later herein.

According to another aspect of the disclosure, the attachment 100 may beprovided with an assist feature 140 to enhance control of the movementof attachment 100, and thus movement of the syringe plunger 241 andpiston 250.1 relative to the syringe barrel 200. Assist feature 140 maybe provided in the form of a traction wheel, which may include arubberized outer member 142 mounted on an inner hub 144. Hub 144 mayinclude extending axles that are received in slots 114.1 and 114.2 inthe attachment main body 110. Assist feature 140 may provide amechanical advantage or leverage to the user during operation. Morespecifically, the user may use their thumb and or finger to rotate theassist feature 140 which may selectively and frictionally engage theflat surface 211 of the syringe body 200. The diameter of the assistfeature 140 provides leverage to the user and allows the user to movethe attachment incrementally using a rolling motion. Referringadditionally to FIG. 4, the assist feature 140 may rest in a disengagedposition shown, where it is slightly above and disengaged from thesyringe flat surface 211. Selective engagement of the assist feature 140may be provided by flexibility (deformation) of the main body 110 of theattachment 100. Alternatively, springs or biasing elements may beincorporated into the axles of hub 144 or into the slots 114.1 and 114.2such that the assist feature 140 engages the surface 211 when a slightdownward force is exerted on the assist feature 140 by the user, anddisengages the surface 211 when user force is removed. FIG. 3illustrates the operation of an example syringe/attachment combinationand shows a position in which the syringe plunger is fully inserted intothe syringe lumen.

According to a further aspect of the disclosure, the attachment and/orsyringe may be provided with features that facilitate the tactilesensing of an incremental dose and movement of the syringe plunger. Forexample, referring to FIG. 2B, the gradation indicia 212 on the syringebarrel flat surface 211 may be provided as raised elements, such asridges or hashes formed in the syringe barrel and of a suitabledimension such that rolling of the assist feature 140 over each ridgegenerates a tactile event, such as a slight resistance and/or clickingsound, that can be sensed by the user. As an alternative, assist featurewheel hub 144 may be provided with a sound generator, such as a toothedelement and a reed element, that generates a clicking sound for anincremental rotation corresponding to one gradation on the syringesurface.

Referring additionally to FIG. 6, in accordance with another aspect ofthe disclosure, attachment 100 may be provided with an optical element150 to enhance the user's viewing of the syringe plunger piston 250.1and gradations 212 and thus enhance precision of operation of thesyringe. Attachment syringe guide end 130 may include a pair of upwardlyextending sidewalls 132, each having a vertical shoulder 134 and lowerhorizontal shoulder 136 which define a receiving space for the opticalelement 150. Optical element 150 may be a magnifying prism made of anoptically transparent material and having magnification properties. Aswill be recognized, the optical element 150 moves with the syringeplunger and thus stays oriented above the syringe plunger piston 250.1as the attachment and plunger move during syringe operation, thusenabling the user to see a magnified view of the plunger piston 250.1and gradations 212 as syringe contents are dispensed/administered. Areference sight line or reticle 180 may be a hairline elementincorporated into or adjacent to the optical element or in theattachment and may provide a precise indication of the syringe plungerpiston movement, even in cases where the piston is not entirely visibleto the user due to syringe wall thickness or material, for example. Asbest seen in FIGS. 3 and 4, a flat bottom surface of optical element 150rests a small distance above the flat surface 211 of the syringe barrel.As will be recognized, this distance enables an accurate reading of thesyringe gradations and plunger movement. Moreover, this distance may beadjusted/selected in order to vary the level of magnification providedby the optical element.

According to yet another aspect of the disclosure, the assist featureand optical enhancement features of the attachment andattachment/syringe combinations contemplated herein include highlycustomizable aspects. Attachment 100 may include two or more mountingslots 114.1 and 114.2 to permit a user to customize the assist featureposition and thus the attachment configuration according to a desiredcomfort level. In addition, assist features 140 may be provided as a kitof several different sized wheels with the attachment to enable the userto select a desired wheel size to achieve precise control for the user'shand, finger or thumb size or other attribute. Likewise, the opticalelement 150 is removable and may be fastened with snap elements/detentsonto the attachment 100 and a kit of optical elements of variousmagnification power may be provided to enable customization according toa user's preferences, or the optical element may be removed to permit auser/physician to use an eye loop or magnifying eyeglasses inconjunction with use of the syringe. As will be recognized, the mountingconfiguration for the assist feature and the optical enhancement featurepermits quick refitting of alternative parts.

FIG. 7 illustrates an alternative attachment configuration 700 in whichthe assist feature is omitted and which facilitates syringe operationusing relative lateral (sliding movement) of a user's thumb and fingers.The main body 710 includes a gripping surface 712 to permit a user toengage the attachment with his or her fingers or thumb and to move theattachment main body, and thus the syringe plunger, relative to thesyringe barrel using sliding movement between the user's thumb andfingers. This mode of actuation provides improved control of thesyringe, enables the user to grip the syringe closer to the injectionpoint (needle end), provides stability to the syringe plunger, andprovides more accurate control of the delivery of syringe contents.

According with yet another aspect, the disclosure provides low-wastesyringe/needle interfaces and syringe plunger piston configurations.FIGS. 8A and 8B are cross-sections showing an example needle hub/syringeinterface and plunger seal advantageous for a syringe having a totalvolume of about 0.25 ml, with the plunger in a slightly open positionand a fully inserted position, respectively. Needle hub 260 includes aneedle 262 mounted therein and an end surface 264 with which the end ofneedle 262 is flush mounted therewith. Needle hub 260 includes an outerthreaded base that engages internal threads on the syringe. Syringe 200includes an internal lumen wall extension 242 that extends into theinterior of needle hub 260 and has an end 243 that forms a sealinginterface with the hub end surface 264. Syringe plunger piston 250.2includes an internal space for receiving a barb-like end 245 of plunger240. Syringe plunger piston 250.2 also includes a flat end surface252.2. As can be seen with additional reference to FIG. 8B, when thepiston is at the full extent of its insert into the syringe lumen, thepiston end surface 252.2 is in abutting contact with the end surface 264of the needle hub, thus eliminating any dead space within the needle huband thus completely evacuating the syringe contents from the lumen. Thismay result in significant cost savings for expensive syringe contents.For delivery of syringe contents, needle 262 may be a 30-gauge needle,which is of a small size and mitigates pain and tissue damage duringinjection. Moreover, one method of operating the device contemplatedherein is to utilize a larger (smaller gauge) needle of a standard, lowcost configuration, such as a standard 20-gauge needle on the syringe,to facilitate quick retrieval of material (i.e., neurotoxin) into thesyringe. Once the syringe is filled, a 30-gauge needle with thelow-waste features described herein may be installed on the syringe andused for delivery.

FIGS. 9A and 9B are cross-sections showing an example needle hub/syringeinterface and plunger seal advantageous for a syringe having a totalvolume of about 0.50 ml, with the plunger in a slightly open positionand a fully inserted position, respectively. In this configuration, thesyringe lumen has an increased diameter compared to the configuration ofFIGS. 8A and 8B. The syringe piston 250.1 may include a first portion253.1 that has a diameter suitable to form a seal with the lumen. Thefirst portion 253.1 may taper down to a smaller diameter portion 254.1that fits within the interior of the lumen end wall, which may be of astandard dimension to fit a standard needle hub 260.

FIG. 10 is an exploded view of an alternative attachment configuration1000 showing an alternative optical element mounting arrangement.Attachment guide end 1030 may include a pair of circular mounting tubes1032 formed therein (one shown in FIG. 10) which receive respectivemounting rods 1152 of a lens mounting frame 1154. A magnifying lens 1150may be mounted within the lens mounting frame. This configuration mayprovide higher magnification of the syringe gradations and referencesight 1080 and may be adjusted to a user's preference.

FIG. 11 is a perspective view of an assembled alternative attachment1100 and syringe 200 according to alternative attachment configuration1100. FIG. 12 is an exploded view of the same embodiment. In thisembodiment, the magnification element 1150 is oriented differently thanin the embodiment of FIG. 1, with a flat side 1152 of the magnifyingelement 1150 facing the assist feature 1140. This configuration providesadditional clearance for the user's thumb when engaging the assistfeature 1140 and provides a viewing angle of the magnified area of thesyringe (the area beneath the magnifying element 1150) that may beergonomically advantageous, i.e., allowing the user to view themagnified areas of the syringe from a direction towards the needle endof the syringe and closer to the area of focus when performinginjections.

FIG. 14 is a bottom perspective view of the attachment/syringecombination of FIG. 11 with the attachment in a “zero” position in whichthe contents of the syringe have been entirely evacuated. As can beseen, the reference sight line or reticle 1180 coincides with thegradation 1402 representing a “zero” or fully emptied position of thesyringe. As will be recognized, the “zero” gradation may be positionedin an offset manner from the zero position of the syringe plunger (i.e.,when it is bottomed against the end wall of the lumen) such that thereticle 1180 and zero gradation 1402 can indicate the fully emptiedposition of the attachment precisely to the user. Referring additionallyto FIG. 15, reticle 1180 may include a filament coated with aconspicuous color, such as red, in order to provide a sharp contrast andenable the user to see the precise location of the plunger (and positionof the attachment relative to the syringe) when the user views themagnified syringe area within the field of view of the magnifyingelement 1150. To further enhance viewing and precision, the attachmentmay include lateral reference shoulders 1182.1 and 1182.2 that coincidewith the reference line or reticle 1180 and enable the user to view theposition of the reticle 1180 from the sides of the syringe. Thereference shoulders 1182.1 and 1182.2 may include a coating in aconspicuous color, such as red, to further define a line of reference onthe attachment. As seen in FIG. 14, the reference shoulder 1182.2 isaligned with the “zero” gradation when the syringe plunger, and thus theattachment, have reached the full extent of their travel relative to thesyringe.

A bottom surface 214 of the syringe 200 may be provided with an opaquecoating that may be of color that results in sharp contrast with thesyringe contents and syringe plunger to provide additional ease ofviewing by the user of the position of the syringe plunger and theplunger/contents interface (demarcation line). The opaque coating maysubstantially cover the lower half of the barrel, or may includepatterns that enhance the user's viewing of the syringe contents andplunger position. For example, an axially extending break may beprovided in the opaque coating directly beneath the lumen where thetranslucency of the syringe barrel allows light to pass to the interiorof the lumen from the syringe barrel underside thereby enhancing theuser's viewing of the syringe contents and plunger position.

FIGS. 16 and 17 illustrate another alternative configuration for asyringe attachment and syringe. This configuration may be useful forprecision dispensing of more viscous syringe contents, such as dermalfillers. In this configuration, the assist feature 1640 may include oneor more toothed elements 1642.1 and 1642.2, such as pinion gears formedon the hub of a circular element, such as a wheel, rotatably mounted inthe attachment main body in a manner as described above with regard toelements 142 and 144 in FIGS. 1 and 2A. The pinion gears 1642.1 and1642.2 cooperate with respective geared rack elements 1280.1 and 1280.2formed on a flat portion 1211 of the syringe barrel 1210. Thisconfiguration, as will be recognized, provides a positive actuation(i.e., no slippage) feature for the syringe attachment relative to thesyringe. A rubber gripping surface 1644 may enhance the user's abilityto rotate the assist feature 1640. Moreover, the assist feature 1640 maybe mounted such that it may be free to rotate (i.e., the pinions are notengaged with the racks) in the absence of lateral pressure (downward inFIG. 16) on the assist feature. This may be accomplished with springelements supporting the wheel 1644 within the mounting slots 1614 (FIG.17) on the attachment, or by making the main body of the attachmentsufficiently flexible that lateral pressure on the assist feature 1640causes deformation of the attachment main body and resulting engagementof the pinion gears with the racks. In this manner, inadvertentactuation of the plunger can be avoided. That is, the user must applylateral pressure to the assist feature before rotating the assistfeature in order for syringe contents to be dispensed. The pitch andprofiles of the pinion teeth and rack teeth may be designed such thateach incremental engagement of a tooth coincides with each gradation onthe syringe, or a predetermined volume of dispensed material. Moreover,the profile of the pinion teeth and rack teeth may provide interference,or may include projections or other features that provide tactile andaudible feedback to the user, i.e., clicking sensation or sound, whichcorresponds to a known incremental dispensed volume or to the gradationson the syringe.

Although the present implementations have been described with referenceto specific example embodiments, it will be evident that variousmodifications and changes may be made to these embodiments withoutdeparting from the broader spirit and scope of the invention as setforth in the claims. Accordingly, the specification and drawings are tobe regarded in an illustrative rather than a restrictive sense.

What is claimed is:
 1. An attachment for controlling the operation of a syringe, the syringe comprising a barrel and a plunger, the attachment comprising: a main body; a syringe plunger engaging end extending from the main body and adapted to engage the syringe plunger; a guide extending from the main body for supporting the main body for movement relative to the syringe barrel; whereby a user may actuate the plunger by movement of the main body relative to the syringe barrel.
 2. The attachment of claim 1, further comprising an assist feature for proving the user with a mechanical advantage in moving the main body relative to the syringe.
 3. The attachment of claim 2, wherein the assist feature includes a rolling element mounted on the main body and having a friction surface for engaging the syringe barrel.
 4. The attachment of claim 2, wherein the assist feature includes at least one toothed element.
 5. The attachment of claim 3, wherein the rolling element is mounted to provide selective engagement of the friction surface with the syringe barrel.
 6. The attachment of claim 3, wherein the main body includes at least two mounting stations for the rolling element to permit a user to adjustably mount the rolling element.
 7. The attachment of claim 1, further comprising a tactile indicator for generating a tactile event to the user as the main body moves incrementally relative to the syringe body.
 8. The attachment of claim 7, wherein the at least one tactile indicator is a rolling element rotatably mounted on the main body and having a friction surface for engaging the syringe barrel.
 9. The attachment of claim 1, further comprising an optical element mounted on the main body for enhancing visualization of gradations on the syringe body.
 10. The attachment of claim 9, wherein the optical element is a magnifying element.
 11. The attachment of claim 9, wherein the optical element includes a bottom flat surface and wherein the main body includes a pair of shoulders for retaining the bottom flat surface a predetermined distance from the syringe barrel surface.
 12. The attachment of claim 1, wherein the guide includes a U-shaped member for engaging an outer surface of the syringe barrel.
 13. A method of controlling the operation of a syringe, the syringe comprising a barrel and a plunger, comprising: providing an attachment having a syringe plunger engaging end and a syringe barrel guide; inserting the syringe barrel into the syringe barrel guide; engaging the syringe plunger with the syringe plunger engaging end; and moving the attachment relative to the syringe barrel to thereby cause the plunger to move relative to the syringe barrel.
 14. The method of claim 13, wherein the step of moving the attachment comprises operating an assist feature on the attachment.
 15. The method of claim 14, wherein the step of operating the assist feature comprises rotating a rotatable element on the attachment.
 16. The method of claim 15, further comprising the step of frictionally engaging the syringe barrel with the rotatable element.
 17. The method of claim 13, further comprising the step of selecting a rotatable element from a group of different sized rotatable elements and installing the selected rotatable element on the attachment.
 18. The method of claim 13, further comprising the step of adjusting the position of a rotatable element on the attachment.
 19. The method of claim 13, further comprising the step of sensing the position of the attachment relative to the syringe barrel by sensing a tactile event generated by the attachment.
 20. The method of claim 13, wherein the step of moving the attachment comprises operating a rotating element having at least one pinion gear and further comprising moving the at least one pinion gear on a rack on the syringe barrel. 